Active character name changed itself

[Alhanelem]

This is most likely due to server merges, and when the server merge occured, your character had the same name as one that already existed on the merged server.

Right now the only way to change names is to create a character on another server with the same name, and when you transfer you'll be required to change it.

You can go on the support site and file a ticket, but the above is probably the only resolution.

This is not the correct place for account/tech support issues. You should file a ticket on the square enix support site. They will move this thread to "not a bug report," so if you'd like to discuss it further, you should use the technical support section. But this is definitely a square enix support thing.